Known window wipers have a wiper arm, which is constructed of a fastening part and a joint part, pivotably connected to it, with a wiper rod. They also have a wiper blade, which is constructed of a support bracket system with a predominant center bracket and pivotably connected, subordinate intermediate brackets as well as claw brackets and a wiper strip. The wiper blade is pivotably connected to the wiper arm, in that a free end of the wiper rod holds a bearing part that is disposed between two side cheeks of the center bracket and that includes a hub that is open over a circumferential region and a pivot bolt of the center bracket. The joint thus formed guides the wiper blade over the window during the pivoting motion; the joint and the support bracket system allow the wiper strip to adapt to adapt to any curvature of the window.
The fastening part of the wiper arm is seated on the free end of a wiper shaft, which is supported in a wiper bearing and is driven by a wiper motor via a crank and a rod linkage. The wiper motor is held by a mounting bracket, which is fastened to a vehicle body and includes the wiper bearing. Often, the wiper bearings themselves act as fastening points, by protruding through openings in the vehicle body and being screwed to the vehicle body with the interposition of vibration-damping rubber-elastic elements. However, it is also possible for them to be connected to the vehicle body via props on the mounting bracket.
The end of the wiper shaft protruding from the vehicle body is a possible cause of injury in the event of accidents involving pedestrians. Proposals for crash regulations by the European Commission (EC III/5021/96 EN), with regard to accidents involving pedestrians, define maximum acceleration values, or so-called head injury criteria, in the region of the vehicle hood at the wiper installation. These criteria can not be met with the conventional wiper installations, even if the vehicle hood covers the wiper shaft, since even in this case, it is still not assured that the spacing between the vehicle hood and the wiper shaft will be large enough, especially when hood gaps are small.
According to the invention, the wiper shaft is displaceable into the vehicle body when an axial force that exceeds a predetermined magnitude is exerted from outside on the end. As a result, on the one hand, the prescribed criteria can be met; on the other, the wiper shaft can be prevented from being displaced by lesser axial forces, for instance if the wiper arm becomes blocked by snow or for other reasons.
Expediently, a defined displacement distance is specified for the wiper shaft. It must be assured here that the displacement distance can be fully utilized, in that the spacing have the wiper arm from the vehicle body or from the windshield, and the spacing of the inner end of the wiper shaft, or of a part solidly connected to it, from an adjacent vehicle part, corresponds at least to the displacement distance. The fastening part of the wiper arm, in the region of its fastening to the wiper shaft, has a large-area cover cap of solid material, in order to reduce the pressure per unit of surface area in the event of an impact on the protruding end of the wiper shaft, and thus to lessen the risk that the end of the wiper shaft will penetrate a person""s body. It is also advantageous that the impact energy is largely dissipated over the displacement distance, because the motion of the wiper shaft is damped to an increased extent over the displacement distance and in particular toward the end of the displacement distance.
For damping the impact, means that deform plastically and/or elastically in the axial direction under the influence of a critical axial force are provided between an inward-acting stop of the wiper shaft and a part solidly connected to the vehicle body, or between such a part in the vehicle body. Such means may be a plastically deformable sheet-metal sheath, which expediently has an axially corrugated region, or they may be thin-walled plate-like elements, which depending on the displacement distance can be disposed multiply, operatively in series. These elements may have so little play from the wiper shaft or other adjacent components that upon their deformation may press against these components and by friction amplify the damping action. Finally, the means can be disposed such that under the influence of the critical axial force, they are upset or pulled apart.
The wiper shaft can be axially secured to the bearing housing of the wiper bearing via positive engagement elements with a rated breaking point, which in response to a critical axial force either break or bend over into a free space. Such rated breaking points can be produced by means of notches, bores, or shearing pins.
In a further feature, the wiper shaft is supported axially inward via an element nonpositively connected to the bearing housing, with the nonpositive engagement dimensioned such that it yields under the influence of a critical axial force. The nonpositive engagement element can be a bushing which is inserted into the bearing housing with a press fit. A bearing bush can expediently be used for the purpose.
A further advantage is that the means are mounted at different points, acting in series. Thus first means can be provided between the wiper shaft and an element, such as a bearing bush, guided in the bearing housing; second means can be provided between that element and the bearing housing; third means can be provided between the bearing housing and the vehicle body or the mounting bracket; and fourth means can be provided between the mounting bracket and the vehicle body.
As a result, on the one hand a long displacement distance with high energy consumption can be attained; on the other, the means can be adapted to one another in such a way that with an increasing critical axial force, they become operative in succession, so that depending on the severity of the accident, only some of the means have to be replaced.